This engine had 335 cubic inch displacement and developed 166 horsepower. However I think that horsepower is a bit on the low side and believe it developed considerably more horsepower.
Don't confuse HP and torque. Prior to 1986 horspower was measure at the crank. This put companies like Ford at a marketing disadvantage.
HP = Torque x RPM
The 589 did a clean 130MPH at 1300 RPM This would mean that the estimated Torque output would be in the range of 450-500 ftlbs maybe a touch more or less. This was actually not uncommon output of the Tractor trailors of the day. The tucker engine was more in line with Big truck thinking than Car thinking engine wise. So the Tucker would be a 300-400 HP car in today's standards.
Since Torque converters were directly attached to the engine on both sides much like a modern TC it doubles the effective torque to the wheel at a peak point.
The Tin Goose would be very interesting to see on a dyno as it ran through the rpm.
I would love to get a copy of the 589 Blue prints because duplicating this engine with some modern advantages. Like computerization of the fuel mix and the hydralic drive valve system. I have a design idea for a "variable compression ratio" which added to the system would allow for easy starts and higher gas mileage. Plus on paper would bump the HP to 700-1000 HP OR gas mileage to 35-48MPG depending on the engine need.